The invention provides an endoscope system, a light source device, and a control method of the endoscope system. The light source device (13) of the endoscope system (10) comprises: a white light source (30) which emits white light used in illumination light for obtaining a common observation image, and a semiconductor light source unit (31). The semiconductor light source unit (31) emits oxygen saturation determining light； the oxygen saturation determining light has a local narrow wavelength domain in the blue region, and when emitted to an observation area, is used for determining the oxygen saturation of hemoglobin in blood in blood vessels at the observation area. Besides the oxygen saturation determining light, the light source device (13) uses light in the red region contained in the white light as blood amount determining light for determining the blood amount in blood vessels, and supplies the light to an electronic endoscope (11). Based on a first and a second camera signal outputted by a camera element according to the oxygen saturation determining light and the blood amount determining light, the blood amount and the oxygen saturation are calculated, and information of both the oxygen saturation and the blood amount is visualized.
